JPH0425716A - Encoder abnormality detecting device - Google Patents

Abstract

PURPOSE:To detect abnormality with high reliability by comparing the count data of an up/down counter which counts up with an A-phase and a B-phase pulse signal with specific constant data. CONSTITUTION:The count data of the up/down counter 15 which counts up with the A-phase pulse signal and B-phase pulse signal outputted by a pulse generator 13 is compared with the specific constant data. When the numeral of the count data exceeds a 1st specific value determined by the quantities of the A-phase pulse signal and B-phase pulse generated when the input shaft of the pulse generator 13 makes one rotation, an abnormality detecting circuit 16 outputs an abnormality detection signal unless the count data value when a Z-phase pulse signal is generated becomes equal to either of a numeral 0 and a 2nd specific value determined by the quantities of the A-phase pulse signal and B-phase pulse signal generated when the input shaft of the pulse generator 13 makes one rotation.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention incorporates a pulse generator that generates three types of pulse signals, A phase, B phase, and A phase, in a sensor main body according to the rotation of an input shaft. The present invention relates to an abnormality detection device for a so-called pulse count type rotary encoder, and particularly to an abnormality detection device for a rotary encoder suitable for controlling industrial robots.

[Conventional technology]

For example, industrial robots require several rotary encoders to control them, but from the viewpoint of cost and signal processing speed, the above-mentioned pulse count type rotary encoders are mainly used as these rotary encoders. is mainly used.

By the way, in such an industrial robot, if the rotary encoder cannot accurately detect the position, the robot will move abnormally and there is a possibility that a dangerous situation will occur.

Therefore, it is necessary to constantly monitor the encoder and prepare for the occurrence of an abnormality, but as a conventional technology for such an encoder abnormality detection device, for example, as described in Japanese Patent Application Laid-Open No. 1-197813, the above-mentioned There is a known device that combines a pulse count type rotary encoder with a so-called absolute type rotary encoder that outputs the detected position as absolute position data, and constantly compares the detection results of these multiple encoders to detect abnormalities. .

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into consideration the fact that a fairly expensive absolute rotary encoder is required in addition to the original encoder, resulting in a significant cost increase.

The purpose of the present invention is to provide a highly reliable system that can reliably detect abnormalities using only the original pulse count encoder.
- To provide a coder anomaly detection device at low cost.

[Means to solve the problem]

In order to achieve the above object, the present invention compares count data of an up/down counter incremented by an A-phase pulse signal and a B-phase pulse signal output from a pulse generator of a pulse count type encoder with predetermined constant data. , when the numerical value of this count data exceeds a first predetermined value determined from the number of A-phase pulse signals and B-phase pulse signals generated when the input shaft of the pulse generator makes one rotation; The count data value at the time when the phase pulse signal is generated is a second predetermined value determined from the number of the A phase pulse signal and the B phase pulse signal generated when the input shaft of the pulse generator makes one revolution; When the value does not match any of the numerical values O, an abnormality detection output is generated.

[Effect]

Looking at the A-phase, B-phase, and Z-phase pulse signals output from the pulse generator that makes up the encoder, we can calculate the number of A-phase and B-phase pulse signals generated when the pulse generator makes one revolution. If N, then the count value of the A-phase and B-phase pulse signals between the two A-phase pulse signals should always be -N, 0, or N.

Therefore, if this count value becomes smaller than -N,
If it becomes larger than N, it means that the A-phase pulse signal was not generated even though the pulse generator rotated more than once; If not, it means that at least one of the A-phase and B-phase pulse signals was not correctly generated despite the rotation of the pulse generator, so an abnormality can be detected by these determinations.

At this time, in the present invention, the A-phase pulse signal and the B-phase pulse signal output from the pulse generator of the encoder,
In addition, since the probability that an abnormality will occur simultaneously in two of the three types of A-phase pulse signals is extremely low, sufficient abnormality detection accuracy can be easily obtained.

〔Example〕

Below, regarding the encoder abnormality detection device according to the present invention,
This will be explained in detail with reference to the illustrated embodiment.

FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to control a motor for driving a manipulator of an industrial robot.
The position command given from the robot control device is sent to the adder IO.
is inputted to the position feedback value and converted into a deviation from the position feedback value, and the motor control circuit 11 outputs a motor current according to this deviation to drive the motor 12. And this motor 1
2 is detected as an A-phase pulse signal and a B-phase pulse signal by the pulse generator 13, and converted into an UP pulse signal and a [)WUN pulse signal by the encoder signal processing circuit 14,
A position feedback value is obtained by inputting it to an up/down counter 15, thereby making it possible to control the motor 12 in accordance with the position command.

Next, 16 is an encoder signal abnormality detection circuit, which inputs the LIP pulse signal outputted from the encoder signal processing circuit 14, the DWUN pulse signal, and the Z-phase pulse signal directly generated from the pulse generator 13. It performs abnormality detection through arithmetic processing, and outputs an encoder abnormality signal when an abnormality occurs.

Reference numeral 17 denotes an abnormality processing circuit which, when an encoder abnormality signal is input from the encoder signal abnormality detection circuit 16, sends a predetermined signal to the control system of the motor 12 in response to the input, and prevents the motor 12 from being driven. Performs predetermined abnormality processing.

Next, the operation of this embodiment will be explained in more detail.

The pulse generator 13 generates three types of pulse signals: A phase, B phase, and Z phase as the motor 12 rotates.
These signals have a relationship as shown in FIG. That is, the A-phase and B-phase pulse signals have a phase difference of 90 degrees from each other, and the phase relationship between these signals is such that when the pulse generator 13 rotates in one direction (positive direction),
The A-phase pulse signal has an advanced phase, and in the opposite direction (negative direction), the B-phase pulse signal has an advanced phase. As described above, N pulse signals of the A phase and B phase are generated during one rotation of the pulse generator 13.

On the other hand, one Z-phase pulse signal is generated every time the pulse generator 13 rotates once, but in this embodiment, the Z-phase pulse signal at this time is
As shown in the figure, the phase pulse signal is generated in synchronization with the A-phase pulse signal.

Next, FIG. 3 shows an embodiment of the encoder signal processing circuit 14, which, as shown, includes two D flip-flops 14a, 14b and one clock signal generator 14.
c, three inverters 14e, 14f, 14g and five AND circuits 14h, 14i, 14j, 14k, 14Q,
14m, and two OR circuits 14n and 14p. At this time, the clock signal generator 1
The frequency of the clock signal 4c is selected to be sufficiently higher than the maximum possible frequency of the A-phase and B-phase pulse signals.

First, the B-phase pulse signal is input to the D flip-flop 14a, and its output is input to the next D flip-flop 1.
4b produces a signal synchronized with the clock signal of this B-phase pulse signal. And these D
By processing the outputs of the flip-flops 14a and 14b with a circuit consisting of inverters 14f and 14g and AND circuits 14h and 14i, rising pulses and rising pulses that appear in synchronization with the clock signal are generated at the rising and falling edges of the B-phase pulse signal, respectively. The falling pulse is AND circuit 1
It is output from 4h and 14i.

Next, these rising pulses and falling pulses are sent to AND circuits 14j to 14m and OR circuits 14n and 14 together with an A-phase pulse signal including the output of inverter 14e.
p, and these OR circuits 14n,
The UP pulse signal and the DOWN pulse signal are respectively obtained from the output of 14p.

Therefore, when the A-phase pulse signal is at level "1" and the B-phase pulse signal rises, the encoder signal processing circuit 14 outputs one pulse of the UP pulse signal, assuming that the encoder has rotated in the positive direction. Conversely, when the A-phase pulse signal is at level "0" and the B-phase pulse signal rises, the encoder is assumed to have rotated in the negative direction and operates to output one pulse of the DOWN pulse signal. As a result, when the encoder rotates once, the number of pulses of each of the UP pulse signal and the DOWN pulse signal becomes 2N.

Next, FIG. 4 shows an embodiment of the encoder signal abnormality detection circuit 16, which, as shown, includes an up/down counter 41, an S-R flip-flop 42, a data latch 43, and four comparators 44. 45, 46, 47, constant setters 48, 49, 50° 51, and OR circuits 48, 50 and NOR circuits 49.

The up/down counter 41 is cleared to a count value of 0 by a reset signal, and has a count value capacity from 2N or more to 12N or less, and functions to perform up-counting with an UP pulse signal and down-counting with a DOWN pulse signal. .

Further, the reset signal of the up/down counter 41 is A
The phase pulse signal and the output signal of the S-R flip-flop 42, which is set by the system reset signal and reset by the A-phase pulse signal, are supplied from the output of the OR circuit 52 to which both signals are input. Therefore, this up/down counter 41 is reset every time an A-phase pulse signal is generated, and the up-down counter 41 is reset every time an A-phase pulse signal is generated, and the up-down counter 41 is reset every time an A-phase pulse signal is generated. The period is also maintained in a reset state. This is because the state of the up/down counter 41 is uncertain during the period from system reset until the A-phase pulse signal is first generated, so there is a risk of erroneous detection.

The count value which is the output of the up/down counter 41 will be supplied to four comparators 44 to 47,
At this time, the count value is directly supplied to the comparator 44, but on the other hand, the remaining comparators 45 to 47 are
- latched in the data latch 43, the latch data D
It will be entered after °.

First, let us look at the comparator 44. Since the count value is directly input to the comparator 44, it is constantly compared with the constant 2N given from the constant setter 48.

As described above, the numerical value N is generated during one rotation of the pulse generator 13, that is, from the generation of the A-phase pulse signal to the generation of the next A-phase pulse signal. This is the number of pulses of the A-phase pulse signal and the B-phase pulse signal.

Therefore, if for some reason the count value exceeds the constant 2N, the comparator 44 generates an output.

Here, if we look at the meaning of this count value exceeding the constant 2N, this means that the up/down counter 41 has not been reset even though the pulse generator 13 (encoder) has rotated at least once. This means that the reset signal was not output from the OR circuit 52, and the cause of this is an abnormality in the A-phase pulse signal. , an abnormality in the A-phase pulse signal can be detected.

Next, regarding the data latch 43, since this data latch 43 uses the A-phase pulse signal as a clock signal, it captures the count value of the up-down counter 41 at each generation timing of the A-phase pulse signal and uses it as the latch data. The latch data D° are sequentially held as data D' and input to comparators 45, 46, and 47, respectively.

First, let's look at the comparator 45. Since a constant is given to the comparator 45 by the constant setter 49, the latch data D' from the comparator 45 becomes a constant (-2N+1). Only when they are equal will an output occur.

Thereafter, similarly, the latch data D is output from the comparator 46.
An output is generated only when ゛ becomes equal to the constant (0), and from the comparator 47, the latch data D ゛ becomes equal to the constant (2N
-1), an output is generated only when it becomes equal to -1).

Since the outputs of these three comparators 45 to 47 are input to the NOR circuit 53, in the end, this NOR circuit 53 calculates the following
An output is generated only when all three conditions (2) and (2) are not satisfied.

■ D' = (-2N+1) ■ D' = (0) ■ D' = (2N-1) First, if we consider the case where these conditions hold, the latch data D' is A Since this data is captured and updated every time a phase pulse signal is generated, this data is based on the A-phase pulses that appear between the generation of the A-phase pulse signal and the generation of the next A-phase pulse signal. This is the number of pulses of the signal and the B-phase pulse signal, that is, the number of pulses of the UP pulse signal and the D○WN pulse signal.

On the other hand, when looking at the behavior of the pulse generator 13 between the generation of the A-phase pulse signal and the generation of the next A-phase pulse signal, it is limited to the following three cases.

(1) After starting rotation in the forward direction, the position where the next A-phase pulse signal is generated is reached without returning to the original rotation start position.

(2) After starting rotation in the positive or negative direction, the next A
When the rotation returns to the original rotation start position without reaching the position where the phase pulse signal is generated.

(3) After starting rotation in the negative direction, the position where the next A-phase pulse signal is generated is reached without returning to the original rotation start position.

Then, only when there is no abnormality in the pulse generator 13 and the A-phase pulse signal, the B-phase pulse signal, and the A-phase pulse signal are correctly generated, any of the above conditions ①, ②, and ② will be satisfied. As a result, the NOR circuit 53 generates an output when an abnormality occurs in the A-phase pulse signal and the B-phase pulse signal.
An abnormality in the human phase pulse signal and the B phase pulse signal can be detected by the output.

The outputs of the comparator 44 and the NOR circuit 53 are each outputted from the OR circuit 5.
In the end, by using the output of this OR circuit 54 as the encoder abnormality signal, even if an abnormality occurs in either the A-phase pulse signal, the B-phase pulse signal, or the A-phase pulse signal, it will be immediately detected. This means that abnormalities can be detected.

Returning to FIG. 1, the encoder abnormality signal output from the encoder signal abnormality detection circuit 16 is input to the abnormality processing circuit 17, where, as already explained, processing such as suppressing the drive of the motor 12 is performed, and the encoder signal abnormality signal is To suppress abnormal robot movements caused by abnormalities and prevent dangerous situations from occurring.

Therefore, according to this embodiment, it is possible to reliably detect an abnormality in the encoder signal without using an absolute rotary encoder, and it is possible to easily ensure the safety of robots and the like at low cost.

Note that in the above embodiment, the encoder signal abnormality detection circuit 1
Although all functions, including 6, are obtained by hardware configuration, this is just one example, and it goes without saying that the present invention can be implemented as software in any grade as required.

〔Effect of the invention〕

According to the present invention, there is no need to install an extra encoder, and
By simply adding a simple signal processing function, it is possible to always reliably detect an abnormality in an encoder signal, so a highly reliable encoder abnormality detection device can be easily provided at low cost.

Further, according to the present invention, if an abnormality occurs in the encoder signal, the abnormality can be reliably detected within the time it takes for the input shaft of the encoder to rotate at most once. In the servo control system of the drive mechanism,
Since abnormality processing can be executed with good responsiveness, it is possible to suppress runaway robot accidents and sufficiently improve safety.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an encoder abnormality detection device according to the present invention, FIG. 2 is a waveform diagram for explaining an encoder signal, and FIG. 3 is a block diagram showing an embodiment of an encoder signal processing circuit. , FIG. 4 is a block diagram showing an embodiment of the encoder signal abnormality detection circuit. 10... Adder, 11... Motor control circuit, 12... Motor, 13... Pulse generator, 14... Encoder signal processing circuit,
15... Up/down counter, 16...
...Encoder signal abnormality detection circuit unloader, 17...
...Abnormality processing circuit. ink haiku haiku

Claims (1)

[Claims] 1. Generate two phase-shifted pulses as an A-phase pulse signal and a B-phase pulse signal every predetermined rotation angle of the input shaft, and generate one pulse at a predetermined rotation angle position during one rotation of the input shaft. a pulse generator that generates the Z-phase pulse signal;
From the phase pulse signal and the B-phase pulse signal, an UP pulse signal is generated when the input shaft rotates in one direction, and a DW signal is generated when the input shaft rotates in the other direction.
A rotary encoder equipped with a signal processing circuit that generates UN pulse signals respectively, an up/down counter that is counted up by the UP pulse signal, counted down by the DOWN pulse signal, and reset by the Z-phase pulse signal; calculation means for comparing the count data of the up-down counter with predetermined constant data, and the count data value is the A-phase pulse signal and the B-phase pulse generated when the input shaft of the pulse generator rotates once. When the count data value exceeds the first predetermined value determined from the number of signals and when the Z-phase pulse signal is generated, the above A occurs when the input shaft of the pulse generator makes one rotation. An encoder characterized in that the arithmetic means generates an abnormality detection output when the second predetermined value determined from the number of phase pulse signals and the number of B-phase pulse signals does not match with either the numerical value 0. Anomaly detection device.